[Feature Request] Add support for casync

[Max Bruckner]

I think that Lennart Pötterings casync would be a useful backend for hard drive and partition images.

https://github.com/systemd/casync

Essentially casync divides a block device (or directory) into content defined junks (similar to rsync) and stores them in a git like data store. The block device is then represented by an index file that contains "pointers" to these chunks in the form of their hashes.

This could be really useful for Clonezilla because it helps to save space.

From a UI perspective Clonezilla should expose some of the command line options and allow the user to specify a directory that will be used as chunk store. This would be especially useful in the following scenarios:

1. When there are multiple similar operating systems on a disk, they share a lot of data and the compression could be much better than with the currently supported sparse image formats.
2. When doing multiple images of the same disk over time, the chunk store can be reused so that only parts that changed will occupy additional disk space.

[Steven Shiau]

Thanks for your suggestion. We will think about how to implement it. Of course, patches are welcom.

Steven